Display modules with direct-lit backlight units

ABSTRACT

A display may have a pixel array such as a liquid crystal pixel array. The pixel array may be illuminated with backlight illumination from a direct-lit backlight unit. The backlight unit may include an array of light-emitting diodes (LEDs) on a printed circuit board. The display may have a notch to accommodate an input-output component. Reflective layers may be included in the notch. The backlight may include a color conversion layer with a property that varies as a function of position. The light-emitting diodes may be covered by a slab of encapsulant with recesses in an upper surface.

This application claims the benefit of provisional patent applicationNo. 63/247,715, filed Sep. 23, 2021, provisional patent application No.63/247,722, filed Sep. 23, 2021, and provisional patent application No.63/247,735, filed Sep. 23, 2021, which are hereby incorporated byreference herein in their entireties.

BACKGROUND

This relates generally to displays, and, more particularly, to backlitdisplays.

Electronic devices often include displays. For example, computers andcellular telephones are sometimes provided with backlit liquid crystaldisplays. Edge-lit backlight units have light-emitting diodes that emitlight into an edge surface of a light guide plate. The light guide platethen distributes the emitted light laterally across the display to serveas backlight illumination.

Direct-lit backlight units have arrays of light-emitting diodes thatemit light vertically through the display. If care is not taken,however, a direct-lit backlight may be bulky or may produce non-uniformbacklight illumination.

SUMMARY

A display may have a pixel array such as a liquid crystal pixel array.The pixel array may be illuminated with backlight illumination from adirect-lit backlight unit. The backlight unit may include an array oflight-emitting diodes (LEDs) on a printed circuit board.

The backlight unit may include first, second, and third light spreadinglayers formed over the array of light-emitting diodes. A colorconversion layer may be formed over the first, second, and third lightspreading layers. First and second brightness enhancement films may beformed over the color conversion layer. A diffusion film may be formedover the brightness enhancement films.

The display may have a notch to accommodate an input-output component.Reflective layers may be included in the notch. An inner surface of ahousing sidewall may have a mitigated reflectance portion. A bracket andfoam may be included in the notch between the optical films and theliquid crystal display panel. A shielding ring may be included in theliquid crystal display panel to mitigate electrostatic discharge. Foammay be included in an upper housing with the same footprint as ahigh-rigidity portion of a lower housing.

The color conversion layer may have a property that varies as a functionof position. The property may be the thickness of a phosphor layer inthe color conversion layer, the concentration of red quantum dots in thecolor conversion layer, the concentration of green quantum dots in thecolor conversion layer, or the concentration of scattering dopants inthe color conversion layer. Protrusions in the optical films may haverounded tips to mitigate scratching and reduce friction between adjacentoptical films.

The light-emitting diodes may be covered by a slab of encapsulant withrecesses in an upper surface. Each recess may overlap a respectivelight-emitting diode. The light-emitting diodes may be arranged incells. Cells may have different sizes in different portions of thebacklight. An adhesive layer having a low dielectric constant andadhesive strips may attach an LED substrate to a housing wall. Aconductive adhesive may also attach the LED substrate to the housingwall.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an illustrative electronic device having adisplay in accordance with an embodiment.

FIG. 2 is a cross-sectional side view of an illustrative display inaccordance with an embodiment.

FIG. 3 is a top view of an illustrative light-emitting diode array for adirect-lit backlight unit in accordance with an embodiment.

FIG. 4 is a cross-sectional side view of an illustrative display havinga direct-lit backlight unit with three light spreading layers, a colorconversion layer, two brightness enhancement films, and a diffusion filmin accordance with an embodiment.

FIG. 5 is a top view of an illustrative light spreading layer showingthe layout of pyramidal protrusions in the light spreading layer inaccordance with an embodiment.

FIG. 6 is a top view of an illustrative display with a notch thataccommodates input-output components in accordance with an embodiment.

FIG. 7A is a top view of an illustrative display with a notch thatincludes reflective patches in accordance with an embodiment.

FIG. 7B is a top view of an illustrative diffusion film that includesreflective patches in accordance with an embodiment.

FIG. 8 is a top view of an illustrative display with a notch that has areflective wall in accordance with an embodiment.

FIG. 9A is a cross-sectional side view of an illustrative display withadhesive patches between optical films, a bracket, and foam inaccordance with an embodiment.

FIG. 9B is a top view of an illustrative optical film with adhesivepatches in accordance with an embodiment.

FIG. 9C is a top view of an illustrative diffusion film with anoverlying bracket in accordance with an embodiment.

FIG. 10 is a cross-sectional side view of an illustrative device with ahousing having an interior wall having a region with mitigatedreflectance in accordance with an embodiment.

FIG. 11 is a cross-sectional side view of an illustrative device havinga shielding ring to mitigate electrostatic discharge in accordance withan embodiment.

FIG. 12A is a top view of an illustrative lower housing having a rigidportion in accordance with an embodiment.

FIG. 12B is a top view of an illustrative upper housing having a foamstructure that overlaps the rigid portion of the lower housing inaccordance with an embodiment.

FIG. 13 is a top view of an illustrative display having electroniccomponents along a lower edge of a LED substrate in accordance with anembodiment.

FIG. 14 is a cross-sectional side view of an illustrative display havinga chassis with a bent portion that protects electronic components alongthe edge of a substrate in accordance with an embodiment.

FIG. 15 is a cross-sectional side view of a color conversion layer withquantum dots and scattering dopants in accordance with an embodiment.

FIG. 16 is a graph illustrating the color variation from alight-emitting diode cell in −Δv′ (negative delta v′), quantifying thebluishness of the light, across the width of the light-emitting diodecell in accordance with an embodiment.

FIG. 17 is a graph illustrating how −Δv′ (negative delta v′),quantifying the bluishness of the light from a display, may vary acrossthe width of the display in accordance with an embodiment.

FIG. 18 is a graph of a color conversion layer property as a function ofa position within a LED cell in accordance with an embodiment.

FIG. 19 is a graph of a color conversion layer property as a function ofa position across a display in accordance with an embodiment.

FIG. 20A is a cross-sectional side view of an illustrative colorconversion layer with a phosphor layer having a varying thickness andcovered by an additional film having a varying thickness in accordancewith an embodiment.

FIG. 20B is a cross-sectional side view of an illustrative colorconversion layer with a phosphor layer having a varying thickness andcovered by an additional film having a uniform thickness in accordancewith an embodiment.

FIG. 21 is a cross-sectional side view of an illustrative colorconversion layer having light-redirecting structures with differentshapes in accordance with an embodiment.

FIG. 22 is a cross-sectional side view of an illustrative backlight withcolor conversion patches formed on an upper surface of a slab ofencapsulant in accordance with an embodiment.

FIG. 23 is a cross-sectional side view of an illustrativelight-redirecting structure with a rounded tip in accordance with anembodiment.

FIG. 24 is a cross-sectional side view of an illustrative backlight unitwith multiple optical films having light-redirecting structures withrounded tips in accordance with an embodiment.

FIG. 25 is a cross-sectional side view of an illustrative light-emittingdiode that emits light with a peak brightness at a non-zero angle inaccordance with an embodiment.

FIG. 26 is a cross-sectional side view of an illustrative backlight unitwith light-emitting diodes covered by an encapsulant layer with recessesover the light-emitting diodes in accordance with an embodiment.

FIGS. 27A-27E are cross-sectional side views showing illustrativerecesses in encapsulant having various shapes in accordance with variousembodiments.

FIG. 28 is a top view of an illustrative LED array having LED cells withvarying pitch in accordance with an embodiment.

FIG. 29 is a cross-sectional side view of an illustrative electronicdevice showing how multiple adhesive layers may attach the LED array toa housing wall in accordance with an embodiment.

FIG. 30 is a top view of an illustrative electronic device showingstrips of adhesive in accordance with an embodiment.

FIG. 31 is a rear view of an illustrative LED array showing howconductive adhesive may be formed around the periphery of the array andan adhesive layer with an array of holes is attached to a centralportion of the LED array in accordance with an embodiment.

DETAILED DESCRIPTION

Electronic devices may be provided with backlit displays. The backlitdisplays may include liquid crystal pixel arrays or other displaystructures that are backlit by light from a direct-lit backlight unit. Aperspective view of an illustrative electronic device of the type thatmay be provided with a display having a direct-lit backlight unit isshown in FIG. 1 . Electronic device 10 of FIG. 1 may be a computingdevice such as a laptop computer, a computer monitor containing anembedded computer, a tablet computer, a cellular telephone, a mediaplayer, or other handheld or portable electronic device, a smallerdevice such as a wrist-watch device, a pendant device, a headphone orearpiece device, a device embedded in eyeglasses or other equipment wornon a user's head, or other wearable or miniature device, a television, acomputer display that does not contain an embedded computer, a gamingdevice, a navigation device, an embedded system such as a system inwhich electronic equipment with a display is mounted in a kiosk orautomobile, equipment that implements the functionality of two or moreof these devices, or other electronic equipment.

As shown in FIG. 1 , device 10 may have a display such as display 14.Display 14 may be mounted in housing 12. Housing 12, which may sometimesbe referred to as an enclosure or case, may be formed of plastic, glass,ceramics, fiber composites, metal (e.g., stainless steel, aluminum,etc.), other suitable materials, or a combination of any two or more ofthese materials. Housing 12 may be formed using a unibody configurationin which some or all of housing 12 is machined or molded as a singlestructure or may be formed using multiple structures (e.g., an internalframe structure, one or more structures that form exterior housingsurfaces, etc.).

Housing 12 may have a stand, may have multiple parts (e.g., housingportions that move relative to each other to form a laptop computer orother device with movable parts), may have the shape of a cellulartelephone or tablet computer, and/or may have other suitableconfigurations. In the arrangement of FIG. 1 , housing 12 includes anupper housing 12A that is rotatably coupled to lower housing 12B. Upperhousing 12A houses display 14 and may therefore sometimes be referred toas display housing 12A. Lower housing 12B houses keyboard 8 and maytherefore sometimes be referred to as keyboard housing 12B. Upperhousing 12A may be coupled to lower housing 12B by hinge structures 18.Upper housing 12A may rotate relative to lower housing 12B around a bendaxis that is colinear with hinge structures 18.

Each one of lower housing 12B and upper housing 12A may be formed ofplastic, glass, ceramics, fiber composites, metal (e.g., stainlesssteel, aluminum, etc.), other suitable materials, or a combination ofany two or more of these materials. Each one of lower housing 12B andupper housing 12A may be formed using a unibody configuration in whichsome or all of that housing is machined or molded as a single structureor may be formed using multiple structures (e.g., an internal framestructure, one or more structures that form exterior housing surfaces,etc.). The arrangement for housing 12 that is shown in FIG. 1 isillustrative.

Display 14 may be a touch screen display that incorporates a layer ofconductive capacitive touch sensor electrodes or other touch sensorcomponents (e.g., resistive touch sensor components, acoustic touchsensor components, force-based touch sensor components, light-basedtouch sensor components, etc.) or may be a display that is nottouch-sensitive. Capacitive touch screen electrodes may be formed froman array of indium tin oxide pads or other transparent conductivestructures.

Electronic device 10 may include additional input-output components inaddition to display 14. As shown in FIG. 1 , electronic device 10 mayinclude a keyboard 8 (including a plurality of keys that are pressed bythe user to provide input) and a touch-sensitive area 6 (that a user maytouch to control the position of a mouse on display 14). Touch-sensitivearea 6 may sometimes be referred to as a touchpad or a trackpad. Thetouch-sensitive area 6 is formed on a surface of lower housing 12B thatis exposed when upper housing 12A is opened to expose display 14.

Display 14 may include an array of pixels 16 formed from liquid crystaldisplay (LCD) components or may have an array of pixels based on otherdisplay technologies. A cross-sectional side view of display 14 is shownin FIG. 2 .

As shown in FIG. 2 , display 14 may include a pixel array such as pixelarray 24. Pixel array 24 (sometimes referred to as a display panel orliquid crystal display panel) may include an array of pixels such aspixels 16 of FIG. 1 (e.g., an array of pixels having rows and columns ofpixels 16). Pixel array 24 may be formed from a liquid crystal displaymodule (sometimes referred to as a liquid crystal display or liquidcrystal layers) or other suitable pixel array structures. A liquidcrystal display panel for forming pixel array 24 may, as an example,include upper and lower polarizers, a color filter layer and a thin-filmtransistor layer interposed between the upper and lower polarizers, anda layer of liquid crystal material interposed between the color filterlayer and the thin-film transistor layer. Liquid crystal displaystructures of other types may be used in forming pixel array 24, ifdesired.

During operation of display 14, images may be displayed on pixel array24. Backlight unit 42 (which may sometimes be referred to as abacklight, direct-lit backlight, direct-lit backlight unit, backlightlayers, backlight structures, a backlight module, a backlight system,etc.) may be used in producing backlight illumination 45 that passesthrough pixel array 24. This illuminates any images on pixel array 24for viewing by a viewer such as viewer 20 who is viewing display 14 indirection 22.

Backlight unit 42 may include a plurality of optical films 26 formedover light-emitting diode array 36. Light-emitting diode array 36 maycontain a two-dimensional array of light sources such as light-emittingdiodes 38 that produce backlight illumination 45. Light-emitting diodes38 may, as an example, be arranged in rows and columns and may lie inthe X-Y plane of FIG. 2 . Light-emitting diodes 38 may be mounted onprinted circuit board 50 (sometimes referred to as substrate 50) and maybe encapsulated by encapsulant 52 (sometimes referred to as transparentencapsulant 52, encapsulant slab 52, etc.). The slab of encapsulant 52may be formed continuously across the LED array and may have a planarupper surface.

Light-emitting diodes 38 may be controlled in unison by controlcircuitry in device 10 or may be individually controlled (e.g., toimplement a local dimming scheme that helps improve the dynamic range ofimages displayed on pixel array 24). The light produced by eachlight-emitting diode 38 may travel upwardly along dimension Z throughoptical films 26 before passing through pixel array 24.

Optical films 26 may include films such as one or more light spreadinglayers 28, color conversion layer 34, one or more brightness-enhancementfilms 44 (sometimes referred to as collimating layers 44), a diffusionfilm 30, and/or other optical films.

Light-emitting diodes 38 may emit light of any suitable color (e.g.,blue, red, green, white, etc.). With one illustrative configurationdescribed herein, light-emitting diodes 38 emit blue light. To helpprovide uniform backlight across backlight unit 42, light fromlight-emitting diodes 38 may be spread by light spreading layer 28. Thelight from the at least one light spreading layer 28 then passes throughcolor conversion layer 34 (which may sometimes be referred to as aphotoluminescent layer).

Color conversion layer 34 may convert the light from LEDs 38 from afirst color to a different color. For example, when the LEDs emit bluelight, color conversion layer 34 may include a phosphor layer (e.g., alayer of white phosphor material or other photoluminescent material)that converts blue light into white light. If desired, otherphotoluminescent materials may be used to convert blue light to light ofdifferent colors (e.g., red light, green light, white light, etc.). Forexample, one layer 34 may have a phosphor layer that includes quantumdots that convert blue light into red and green light (e.g., to producewhite backlight illumination that includes, red, green, and bluecomponents, etc.). Configurations in which light-emitting diodes 38 emitwhite light (e.g., so that layer 34 may be omitted, if desired) may alsobe used.

By the time light from light-emitting diodes 38 reaches the one or morebrightness-enhancement films 44, the light has been converted from blueto white and has been homogenized (e.g., by the light spreading layer).Brightness-enhancement films 44 may then collimate off-axis light toincrease the brightness of the display for a viewer viewing the displayin direction 22. Diffusion film 30 may further diffuse the light tohomogenize the light ultimately provided to pixel array 24.

FIG. 3 is a top view of an illustrative light-emitting diode array forbacklight 42. As shown in FIG. 3 , light-emitting diode array 36 maycontain rows and columns of light-emitting diodes 38. Eachlight-emitting diode 38 may be associated with a respective cell (tilearea) 38C. The length D of the edges of cells 38C may be 2 mm, 18 mm,1-10 mm, 1-4 mm, 10-30 mm, more than 5 mm, more than 10 mm, more than 15mm, more than 20 mm, less than 25 mm, less than 20 mm, less than 15 mm,less than 10 mm, less than 1 mm, less than 0.1 mm, greater than 0.01 mm,greater than 0.1 mm, or any other desired size. If desired, hexagonallytiled arrays and arrays with light-emitting diodes 38 that are organizedin other suitable array patterns may be used. In arrays with rectangularcells, each cell may have sides of equal length (e.g., each cell mayhave a square outline in which four equal-length cell edges surround arespective light-emitting diode) or each cell may have sides ofdifferent lengths (e.g., a non-square rectangular shape). Theconfiguration of FIG. 3 in which light-emitting diode array 36 has rowsand columns of square light-emitting diode regions such as cells 38C ismerely illustrative.

If desired, each cell 38C may have a light source that is formed form anarray of light-emitting diode dies (e.g., multiple individuallight-emitting diodes 38 arranged in an array such as a 2×2 cluster oflight-emitting diodes in cell 38C). For example, light source 38′ in theleftmost and lowermost cell 38C of FIG. 3 has been formed from a 2×2array of light-emitting diodes 38 (e.g., four separate light-emittingdiode dies). In general, each cell 38C may include a light source 38′with a single light-emitting diode 38, a pair of light-emitting diodes38, 2-10 light-emitting diodes 38, at least two light-emitting diodes38, at least 4 light-emitting diodes 38, at least eight light-emittingdiodes 38, fewer than five light-emitting diodes 38, or other suitablenumber of light-emitting diodes. Illustrative configurations in whicheach cell 38C has a single light-emitting diode 38 may sometimes bedescribed herein as an example. Illustrative configurations in whicheach cell 38C has four light-emitting diodes 38 may also sometimes bedescribed herein as an example. These examples are, however, merelyillustrative. Each cell 38C may have a light source 38 with any suitablenumber of one or more light-emitting diodes 38. When multiple LEDs areincluded in a single cell, the multiple LEDs may be controlled in unison(e.g., to have the same brightness). The diodes 38 in light-emittingdiode array 36 may be mounted on a printed circuit board substrate (50)that extends across array 36 or may be mounted in array 36 using othersuitable arrangements.

As previously mentioned, more than one light spreading layer 28 and morethan one brightness-enhancement film may be included in the opticalfilms 26 of the backlight unit 42. FIG. 4 is a cross-sectional side viewof an illustrative display having three light spreading layers, twobrightness-enhancement films, and one diffusion film.

As shown in FIG. 4 , a first light spreading layer 28-1, a second lightspreading layer 28-2, and a third light spreading layer 28-3 are formedbetween light-emitting diode array 36 and color conversion layer 34.Each light spreading layer has a similar structure, with protrusions(sometimes referred to as prisms or light-redirecting structures)extending from a substrate (base film). Light spreading layer 28-1includes protrusions 102-1 that extend from substrate 104-1. Lightspreading layer 28-2 includes protrusions 102-2 that extend fromsubstrate 104-2. Light spreading layer 28-3 includes protrusions 102-3that extend from substrate 104-3.

Substrates 104-1, 104-2, and 104-3 may sometimes be referred to as basefilm portions and may be formed from a transparent material such aspolyethylene terephthalate (PET) or any other desired material.Light-redirecting structures 102-1, 102-2, and 102-3 may be formed fromthe same material as base film portions 104-1, 104-2, and 104-3 or maybe formed from a different material than the base film portion.Different materials may be used in each light spreading layer if desiredor the light spreading layers may be formed from the same material(s).

For each light spreading layer, the protrusions 102 may be formed in anarray across the light spreading layer. Each protrusion 102 (sometimesreferred to as light-redirecting structure 102 or prism 102) may splitan incoming point light source into three or more points. Theprotrusions may have a pyramidal shape (e.g., with a square base andfour triangular faces that meet at a vertex), a triangular pyramidalshape (e.g., with a triangular base and three triangular faces that meetat a vertex), partial-cube shape (e.g., corner-cubes by three squarefaces that meet at a vertex), a tapered pyramid structure (where eachface of the pyramid has an upper portion and a lower portion that are atan angle relative to one another), or any other desired shape.Square-based pyramidal protrusions may split a point light source intofour points, whereas triangular pyramidal protrusions may split a pointlight source into three points.

FIG. 5 is a top view of light spreading layer 28-1 showing howprotrusions 102-1 may be arranged in an array. In this case, eachprotrusion has a pyramidal shape with a square base and four triangularfaces that meet at a vertex 106.

The example in FIGS. 4 and 5 of the light-redirecting structures 102being formed from protrusions from a substrate is merely illustrative.In another possible arrangement, the light-redirecting structures may beformed as recesses in the corresponding substrate film 104. The recessesmay have any desired shape (e.g., a square-based pyramidal shape, atriangular-based pyramidal shape, etc.). Additionally, the example inFIG. 4 of light-redirecting structures 102 being formed on the lowersurface of the light-redirecting layers is merely illustrative.Light-redirecting structures 102 may alternatively be formed on theupper surface in one or more of the light-redirecting layers.

Substrates 104-1, 104-2, and 104-3 in FIG. 4 may each have a matte uppersurface (e.g., the surface that is higher in the positive Z-directionmay be matte). The matte upper surface may mitigate undesiredreflections in the backlight unit.

Light spreading layer 28-3 (e.g., substrate 104-3 and/or prisms 102-3)may be formed from a diffusive material such that light travelling alongthe Z-axis is diffused by light spreading layer 28-3. In contrast, lightspreading layers 28-1 and 28-2 are not formed from diffusive material.In one arrangement, substrate 104-3 is formed from an entirely different(and more diffusive) material than substrate 104-2 and 104-1. In anotherpossible arrangement, substrates 104-1, 104-2, and 104-3 are formed fromthe same base material and substrate 104-3 includes an additive thatincreases the diffusion of substrate 104-3 relative to substrates 104-1and 104-2 (which do not include the diffusion-increasing additive).

As shown in FIG. 4 , color conversion layer 34 may include a phosphorlayer 40 (e.g., a layer of white phosphor material or otherphotoluminescent material) that converts blue light into white light. Ifdesired, other photoluminescent materials may be used to convert bluelight from LEDs 38 to light of different colors (e.g., red light, greenlight, white light, etc.). For example, phosphor layer 40 may includered quantum dots 112-R that convert blue light into red light and greenquantum dots 112-G that convert blue light into green light (e.g., toproduce white backlight illumination that includes, red, green, and bluecomponents, etc.).

In addition to phosphor layer 40, color conversion layer 34 may includea partially reflective layer 41. Partially reflective layer 41(sometimes referred to as a dichroic layer or dichroic filter layer) mayreflect all red and green light and partially reflect blue light, forexample. Partially reflective layer 41 therefore allows for some of theblue light to be recycled through optical films 26.

An additional film such as film 108 may also be included in the colorconversion layer. The additional film 108 (sometimes referred to as anoptical film, substrate, base film, etc.) may be formed from a polymermaterial (e.g., polyethylene terephthalate). Light-redirectingstructures such as protrusions 102-4 may be formed on an upper surfaceof additional film 108. Protrusions 102-4 may have any one of thearrangements described above in connection with protrusions 102-1,102-2, and 102-3 (e.g., an array of pyramids as shown in FIG. 5 ).Light-redirecting structures 102-4 may be formed from the same materialas film 108 or may be formed from a different material than the film108.

In the example of FIG. 4 , a first brightness and enhancement film 44-1and a second brightness-enhancement film 44-2 are included in thebacklight unit. Each brightness-enhancement film has a similarstructure, with protrusions (sometimes referred to as prisms orlight-redirecting structures) extending from a substrate (base film).Brightness-enhancement film 44-1 includes protrusions 110-1 that extendfrom substrate 114-1. Brightness-enhancement film 44-2 includesprotrusions 110-2 that extend from substrate 114-2.

Substrates 114-1 and 114-2 may sometimes be referred to as base filmportions and may be formed from a transparent material such aspolyethylene terephthalate (PET) or any other desired material.Light-redirecting structures 110-1 and 110-2 may be formed from the samematerial as base film portions 114-1 and 114-2 or may be formed from adifferent material than the base film portions. Different materials maybe used in each brightness-enhancement film if desired or the lightspreading layers may be formed from the same material(s).

In each brightness-enhancement film, the protrusions 110 may extend instrips across the light spreading layer. For example, protrusions 110-1may be elongated, parallel protrusions (sometimes referred to as ridges)that extend along a longitudinal axis across the layer (e.g., parallelto the Y-axis in FIG. 4 ). Protrusions 110-2 may have a similarstructure as protrusions 110-1 (with elongated, parallel protrusionsextending across the brightness-enhancement film). Protrusions 110-2 maybe rotated (e.g., by 90°) relative to the protrusions 110-1.

As yet another possible arrangement, protrusions 110-1 may have any oneof the arrangements described above in connection with protrusions102-1, 102-2, and 102-3 (e.g., an array of pyramids as shown in FIG. 5). Similarly, protrusions 110-2 may have any one of the arrangementsdescribed above in connection with protrusions 102-1, 102-2, and 102-3(e.g., an array of pyramids as shown in FIG. 5 ).

The example in FIG. 4 of the light-redirecting structures 110 beingformed from protrusions from a substrate is merely illustrative. Inanother possible arrangement, the light-redirecting structures 110 maybe formed as recesses in the corresponding substrate film 114.Additionally, the example in FIG. 4 of light-redirecting structures 110being formed on the upper surface of the brightness-enhancement films ismerely illustrative. Light-redirecting structures 110 may alternativelybe formed on the lower surface in one or more of thebrightness-enhancement films.

In FIG. 4 , each adjacent pair of optical films may be separated by anair gap. The air gap may provide a refractive index difference as lightenters and exits each optical film, ensuring the light from LEDs 38 isspread by the light spreading layers 28 (e.g., via refraction and/ordiffraction). Alternatively, instead of including air gaps between theoptical films, a low-index filler material may be formed between eachadjacent optical film.

FIG. 6 is a top view of display 14 showing how the display may have afootprint with a notch along one of its edges. As shown in FIG. 6 ,display 14 has left and right edges that are connected by upper andlower edges. Along the upper edge of the display, a notch 62 is present.One or more input-output components 64 is included in the region ofnotch 62. Input-output components 64 may include sensors components suchas a camera or an ambient light sensor, light-emitting components, orany other desired input-output components.

LEDs for backlight unit 42 and/or other display components are omittedin notch 62. In other words, every layer of display 14 (e.g., the liquidcrystal display panel, the optical films, the LED array, etc.) mayoptionally have a respective notch in region 62 to accommodateinput-output components 64. As a result, no light is emitted by display14 in notch 62. Additionally, the area of display 14 adjacent to notch62 (e.g., area 66 in FIG. 6 ) may be dimmer than the remaining portionsof display 14. To better illuminate this area and ensure the display hasa uniform brightness adjacent to notch 62 as in other portions of thedisplay, one or more reflective layers may be incorporated in notch 62.

FIG. 7A is a top view of display 14 showing LED array 36. As shown inFIG. 7A, there is a notch in the LED array (e.g., a notch in printedcircuit board 50) where no backlight LED components are present.Input-output components 64 may be formed in notch 62. The input-outputcomponents may be formed on a substrate 72 (e.g., a printed circuit orother desired substrate). The display may also include protrusions 68(sometimes referred to as alignment structures 68, attachment structures68, alignment protrusions 68, attachment structures 68, etc.).Protrusions 68 may protrude into recesses in one or more optical films26 for the backlight unit 42. In this way, protrusions 68 align theoptical films 26 for the backlight unit and ensure the optical films 26do not undesirably shift during operation of the electronic device.Protrusions 68 may be formed integrally with upper housing 12A (see FIG.1 ) or may be separate structures that are attached to upper housing12A.

To increase the luminance in regions of the display adjacent to notch62, reflective layers 70 may be formed in notch 62. In the example ofFIG. 7A, first and second reflective layers (sometimes referred to asreflective patches) are incorporated on either side of substrate 72. Thefirst and second reflective layers are therefore formed on first andsecond opposing sides of notch 62. The reflective layers 70 andsubstrate 72 may be coplanar. The reflective layers 70 and LED array(e.g., substrate 50, LEDs 38, and/or encapsulant 52) may be coplanar.Each reflective layer 70 may have an opening that receives acorresponding protrusion 68. In other words, each protrusion 68protrudes through the opening in a respective reflective layer.

Reflective layers 70 may be formed from white ink, metal, or any otherdesired material. Reflective layers 70 may have a reflectance that isgreater than 50%, greater than 60%, greater than 70%, greater than 80%,greater than 90%, etc. Reflective layers 70 may therefore recycle lightemitted from the active area of the backlight unit/display back into theactive area to increase luminance in region 66 adjacent to the notch,increasing display uniformity around the notch.

FIG. 7B is a top view of diffuser film 30 for backlight unit 42. Inaddition to reflective layers 70, display 14 may include reflectivelayers 74 on diffuser film 30. Diffuser film 30 may have openings 76that receive protrusions 68. In other words, protrusions 68 protrudethrough the openings 76 in diffuser film 30, thus maintaining theposition of diffuser film 30.

The dashed line shows the position of the LED array 36 relative todiffuser film 30. As shown, diffuser film 30 includes portions thatoverlap the notch 62 in the LED array. These portions of the diffuserfilm 30 may overlap reflective layers 70. The width of the notch indiffuser film 30 is therefore less than the width of the notch in LEDarray 36.

First and second reflective layers 74 (sometimes referred to asreflective patches 74) are formed on diffuser film 30 on either side ofthe notch in the diffuser film. Each reflective layer 74 may have afootprint that overlaps a footprint of a corresponding, underlyingreflective layer 70. Reflective layers 74 may be formed from white ink,metal, or any other desired material. Reflective layers 74 may have areflectance that is greater than 50%, greater than 60%, greater than70%, greater than 80%, greater than 90%, etc. Reflective layers 74 maytherefore recycle light emitted from the active area of thebacklight/display back into the active area to increase luminance inregion 66 adjacent to the notch, increasing display uniformity aroundthe notch.

As shown in FIG. 7B, each reflective patch 74 may accommodate arespective opening 76 in the diffusion film 30. In other words, thediffusion film 30 has an upper edge. A notch is formed in the upper edgeof diffusion film 30. Diffusion film 30 has side edges and an inset edgethat define the notch in the diffusion film 30. A first portion ofreflective patch 74 is formed between a respective opening 76 and theupper edge of the diffusion film 30. A second portion of reflectivelayer 74 is formed between a respective opening 76 and a respective side(notch-defining) edge of the diffusion film 30.

In FIG. 7A, reflective layer 70 may have a width (e.g., the dimensionparallel to the X-axis), length (e.g., the dimension parallel to theY-axis) and height/thickness (e.g., the dimension parallel to theZ-axis). In FIG. 7A, the reflective layer 70 has a width and length thatare greater than the thickness of the reflective layer. However, thisexample is merely illustrative. In another desired arrangement, shown inFIG. 8 , reflective layer 70 has a width and/or length that is smallerthan the thickness of the reflective layer.

As shown in FIG. 8 , reflective layer 70 may be formed in notch 62 atthe interface between the notch and the active area of display 14. Inother words, reflective layer 70 is formed along the border of LED array36 within the notch. Reflective layer 70 may be sufficiently thick to beadjacent to the edges of one or more optical films 26 in addition to LEDarray 36. In other words, the height of reflective layer 70 may be equalto or greater than the height of the optical film stack such that theedge of each optical film is adjacent to a portion of reflective layer70. This may result in the same boundary condition for display 14 alongnotch 62 as along the remaining display edges (where the display andoptical films are adjacent to a housing wall of upper housing 12A). As aresult, the reflection performance is consistent in notch 62 as theother active area edges, resulting in a uniform luminance adjacent tonotch 62.

Reflective layer 70 in FIG. 8 (sometimes referred to as reflective wall70) may be formed integrally with display housing 12A or may be formedfrom a separate structure that is attached to display housing 12A.Reflective layer 70 in FIG. 8 may have a reflectance that is greaterthan 40%, greater than 50%, greater than 60%, greater than 70%, greaterthan 80%, greater than 90%, etc.

The reflective wall in FIG. 8 may extend along the entire notch 62(e.g., first, second, and third edges of the display that define notch62) or may be discontinuous within notch 62. For example, the reflectivewall may have two or more portions separated by gaps. As an example,first and second portions of the reflective wall may be separated by agap in region 80 in FIG. 8 .

In the arrangement of FIG. 8 , reflective wall 70 may serve as aprotrusion that aligns optical films 26 within the backlight unit. Inother words, optical films 26 may have openings that align withreflective wall 70 such that reflective wall 70 secures the position ofoptical films 26.

FIG. 7A shows an example where protrusions 68 are used to secure opticalfilms within the display. However, other structures may additionally orinstead be used to secure optical films 26 within display 14.

FIG. 9A is a cross-sectional side view of display 14 in notch region 62showing how adhesive patches may be included between optical films inthe display to ensure the optical films do not move or rotate duringoperation of the electronic device. FIG. 9A shows LED array 36 formedover a wall of housing 12A. A portion of LED array 36 is omitted innotch region 62. Substrate 72 (with input-output components 64 as shownin FIG. 7A) and reflective patches 70 are included in the notch in LEDarray 36.

Optical films 26 including light spreading layer 28-1, light spreadinglayer 28-2, light spreading layer 28-3, color conversion layer 34,brightness-enhancement film 44-1, brightness-enhancement film 44-2, anddiffusion film 30 are formed over LED array 36. The optical films mayhave one or more portions that overlap some of notch region 62 (e.g., asshown with diffusion film 30 in FIG. 7B).

To prevent rotation, movement, and/or wrinkling of the optical films,first and second adhesive patches 82 are formed betweenbrightness-enhancement film 44-1 and brightness-enhancement film 44-2.Additionally, first and second adhesive patches 84 are formed betweenbrightness-enhancement film 44-2 and diffusion film 30. A firstreflective patch 70, a first adhesive patch 82, and a first adhesivepatch 84 (e.g., on the left in FIG. 9A) may have footprints that overlapin the Z-direction. A second reflective patch 70, a second adhesivepatch 82, and a second adhesive patch 84 (e.g., on the right in FIG. 9A)may also have footprints that overlap in the Z-direction.

As shown in FIG. 9A, display 14 may also include a bracket 86 and foam88 between the upper-most optical film (diffusion film 30) and thebottom of pixel array 24 (sometimes referred to as display panel 24). Afirst layer of adhesive 90 is interposed between an upper surface ofdiffusion film 30 and a lower surface of bracket 86. Bracket 86 mayapply compressive force on the optical films 26 (e.g., in the negativeZ-direction) to keep the optical films from sliding off alignmentprotrusions 68. Bracket 86 may have one or more openings to accommodateinput-output components 64 that are formed in the notch region. Bracket86 may be formed from stainless steel or another desired rigid material.A second layer of adhesive 92 is interposed between an upper surface ofbracket 86 and a lower surface of foam 88. Foam 88 may be formed from acompressive material and applies compressive force on the optical films26 (e.g., in the negative Z-direction) to keep the optical films fromsliding off alignment protrusions 68. Foam 88 also fills the gap betweenpixel array 24 and the optical films 26, thus preventing deflection inthe Z-direction of the pixel array and improving the structuralintegrity of the display.

Similar to as shown by openings 76 in diffusion film 30 in FIG. 7B, eachoptical film 26 may have openings to accommodate protrusions 68 (e.g.,in FIG. 7A). The alignment of the optical films is maintained by theprotrusions 68.

FIG. 9B is a top view of an illustrative optical film with adhesivepatches on the top surface. Specifically, FIG. 9B is a top view ofbrightness-enhancement film 44-1 for backlight unit 42. As shown,brightness-enhancement film 44-1 may have openings 94 that receiveprotrusions 68. In other words, protrusions 68 protrude through theopenings 94 in brightness-enhancement film 44-1, thus maintaining theposition of brightness-enhancement film 44-1.

The dashed line shows the position of the LED array 36 relative tobrightness-enhancement film 44-1. As shown, brightness-enhancement film44-1 includes portions that overlap the notch 62 in the LED array. Theseportions of the brightness-enhancement film 44-1 may overlap reflectivelayers 70 (see FIGS. 7A and 9A). The width of the notch inbrightness-enhancement film 44-1 is less than the width of the notch inLED array 36. The optical films may all have a notch with the same orsimilar dimensions as the notch shown in FIG. 9B.

First and second adhesive patches 82 (sometimes referred to as adhesivelayers 82) are formed on brightness-enhancement film 44-1 on either sideof the notch in the brightness-enhancement film 44-1. Each adhesivelayer 82 may have a footprint that overlaps a footprint of acorresponding, underlying reflective layer 70.

As shown in FIG. 9B, each adhesive patch 82 may accommodate a respectiveopening 94 in the brightness-enhancement film 44-1. In other words, thebrightness-enhancement film 44-1 has an upper edge. A notch is formed inthe upper edge of brightness-enhancement film 44-1.Brightness-enhancement film 44-1 has side edges and an inset edge thatdefine the notch in the brightness-enhancement film 44-1. A firstportion of adhesive layer 82 is formed between a respective opening 94and the upper edge of the brightness-enhancement film 44-1. A secondportion of adhesive layer 82 is formed between a respective opening 94and a respective side (notch-defining) edge of thebrightness-enhancement film 44-1.

Brightness-enhancement film 44-2 may have the same or similar footprintas brightness-enhancement film 44-1. Similarly, adhesive patches 84 onbrightness-enhancement film 44-2 may have the same or similararrangement as adhesive patches 82 on brightness-enhancement film 44-1.In other words, each adhesive patch 84 may accommodate a respectiveopening and may overlap with a respective reflective layer 70 (andrespective adhesive patch 82).

FIG. 9C is a top view of diffusion film 30 showing the position ofbracket 86 relative to the notch and openings in the diffusion film. Asshown, bracket 86 extends over the notch and has a portion that coversthe notch of the optical films and LED array. The portion of bracket 86in the notch has openings 96 that accommodate input-output components 64that are positioned in the notch. In other words, input-outputcomponents 64 may have a thickness in the Z-direction that protrudesthrough openings 96 in the bracket 86. First and second opposing sidesof the bracket 86 overlap the diffusion film 30 and other optical films26 in the backlight unit. The bracket does not overlap openings 76 inthe diffusion film (and the other corresponding openings in the opticalfilms that are aligned with openings 76).

Foam 88, meanwhile, extends over the notch and has a portion that coversthe notch of the optical films and LED array. The portion of foam in thenotch has openings with the same footprint as bracket openings 96. Theopenings in the foam accommodate input-output components 64 that arepositioned in the notch. In other words, input-output components 64 mayhave a thickness in the Z-direction that protrudes through the openingsin the foam 88. First and second opposing sides of the foam 88 overlapthe diffusion film 30 and other optical films 26 in the backlight unit.Unlike bracket 86, foam 88 overlaps openings 76 in the diffusion film(and the other corresponding openings in the optical films that arealigned with openings 76).

FIG. 10 is a cross-sectional side view of display 14. FIG. 10 shows howdisplay 14 is formed within display housing 12A. Display 12A has anexterior surface 142 that forms an exterior (outer-most) surface of theelectronic device 10 and an interior surface 144. Interior surface 144may define a cavity that contains the backlight unit 42 and pixel array24 for display 14.

As shown in FIG. 10 , optical films 26 may be formed over LED array 36within display housing 12A. Optical films 26 and LED array 36 may beparallel to a rear wall 146 of the display housing. The rear wall 146(sometimes referred to as rear wall portion 146) extends parallel to theXY-plane. In addition to rear wall 146, display housing 12A has asidewall portion 148 (sometimes referred to as sidewall 148) thatextends in the Z-direction. Sidewall portion 148 has a portion 150 ofinterior surface 144 that faces the optical films 26.

FIG. 10 additionally shows how a spacer 152 may be formed between LEDarray 36 and optical films 26. Spacer 152 may optionally be an adhesivespacer. Similarly, a spacer 154 may be formed between housing 12A andpixel array 24. Spacer 154 may optionally be an adhesive spacer. Theelectronic device also includes a trim structure 156. Trim structure 156may have a rounded upper surface.

To minimize the width of the border region of the display, the edges ofoptical films 26 may be positioned very close to portion 150 of interiorsurface 144 of display housing 12A. The magnitude of gap 158 between theedge of films 26 and interior surface 144 may be less than 30millimeters, less than 15 millimeters, less than 10 millimeters, lessthan 5 millimeters, less than 3 millimeters, less than 2 millimeters,less than 1 millimeter, less than 0.5 millimeters, less than 0.3millimeters, less than 0.1 millimeters, less than 0.05 millimeters, etc.

If care is not taken, light may exit the edges of optical films 26 andreflect off of the interior surface 144 of display housing 12A towards aviewer. This may cause the edge of the display to have a blue tint,particularly at off-axis viewing angles. To mitigate this issue, portion150 of interior surface 144 of housing 12A may be treated or coated tomitigate the reflectance of portion 150.

As one example, portion 150 of housing 12A may be laser treated tomitigate the reflectance of the housing 12A. Housing 12A may be formedfrom a metal material such as aluminum. Laser darkening may be performedon the aluminum housing to reduce reflectance. The example of usinglaser darkening to mitigate the reflectance in portion 150 of housing12A is merely illustrative. A double anodization technique may insteadbe used if desired. As yet another example, a black or gray ink or aless reflective metal than the rest of housing 12A may be coated/platedon the housing in region 150.

Ultimately, portion 150 of interior surface 144 of housing 12A may havea lower reflectance (at visible light wavelengths) than the adjacentportions of interior surface 144. Portion 150 of interior surface 144 ofhousing 12A may also have a lower reflectance than exterior surface 142of housing 12A. The reflectance in portion 150 may be selected to besufficiently low to mitigate the blue tint in the display at off-axisviewing without causing a dark edge in the display. The reflectance inportion 150 may be greater than 20%, greater than 30%, greater than 35%,greater than 40%, greater than 50%, less than 80%, less than 60%, lessthan 50% less than 45%, less than 40%, between 35% and 45%, between 30%and 50%, etc. The difference in reflectance between portion 150 ofhousing 12A and the adjacent/remaining portions of housing 12A may begreater than 10%, greater than 20%, greater than 30%, greater than 40%,greater than 50%, between 30% and 50%, etc. As one specific example,portion 150 may have a reflectance between 35% and 45% while the rest ofhousing 12A has a reflectance between 70% and 80%. In some cases, thebulk of housing 12A may have a reflectance that is within the targetrange for portion 150. Therefore, portion 150 may match the rest of thehousing (because no modification is required to optimize the reflectancein portion 150). For example, the entire housing 12A may have areflectance between 35% and 45%.

FIG. 11 is a cross-sectional side view of display 14 showing additionaldetails regarding trim structure 156 and pixel array 24. As shown inFIG. 11 , pixel array 24 includes a polarizer 172, first substrate 160(e.g., a thin-film transistor substrate), one or more layers 162 thatare formed over substrate 160, a sealant 164 that is formed over layers162, one or more layers 166 that are formed over sealant 164, a secondsubstrate 168 (e.g., a color filter substrate) that is formed overlayers 166, and a polarizer 170 that is formed over substrate 168.

Polarizers 170 and 172 may be linear polarizers that control the lightemitted by the liquid crystal display. Polarizer 172 (sometimes referredto as a lower polarizer or rear polarizer) may ensure light enters thedisplay panel with a uniform polarization. A liquid crystal layer may beformed between substrates 168 and 160 (e.g., coplanar with sealant 164).Thin-film transistor circuitry within substrate 160 may control theliquid crystal layer in the display to selectively rotate or not rotatethe polarization of the light. Light that exits the liquid crystal layerwith a polarization aligned with the pass-axis of polarizer 170 willexit the display and be viewable to a user. Light that exits the liquidcrystal layer with a polarization not aligned with the pass-axis ofpolarizer 170 will be blocked and not be viewable to a user. Layers 162may include multiple dielectric layers (e.g., passivation layers, liquidcrystal alignment layers, etc.). Layers 166 may include multipledielectric layers (e.g., adhesive layers, liquid crystal alignmentlayers, black masking layers, etc.). An additional encapsulant material174 (sometimes referred to as potting 174) may be formed along the edgeof display panel 24. Color filter substrate 168 may include an array ofcolor filter elements that impart desired colors to the light emitted bypixels within the display panel.

A first spacer 154 may be formed between housing 12A and display panel24. Spacer 154 may optionally be an adhesive spacer. A second spacer 176may be formed between housing 12A and display panel 24. Spacer 176 mayoptionally be an adhesive spacer. Spacers 154 and 176 may directlycontact substrate 160. Trim structure 156 may be attached to housing 12Awith an adhesive layer 178. Trim structure 156 may have a rounded uppersurface.

To minimize the width of the non-light-emitting border of display 14,pixel array 24 may include traces that are close to the display edges,making the display susceptible to electrostatic discharge (ESD) damage.To prevent electrostatic discharge damage, a shield ring 180 may beformed around the periphery of the display. Shield ring 180 may have aring shape with a footprint that matches the footprint of the edges ofthe display (e.g., the shield ring extends around the entire peripheryof the display and accommodates the notch). Shield ring 180 thereforehas a central opening in which the active area of the display is formed.Shield ring 180 may be electrically connected to ground and thereforemay sometimes be referred to as grounding ring 180.

Additionally, to prevent electrostatic discharge damage, sealant 164 mayoverlap the metal traces on the edge of substrate 160. Thin-filmtransistor substrate 160 may include a number of metal traces that formthin-film transistor circuitry for the display. Sealant 164 may extendto the edge of the display panel to overlap ground ring 180 and othertraces at the edges of the display panel. As previously mentioned,sealant 164 may be a liquid crystal sealant that contains the liquidcrystal layer within the display.

Trim structure 156 may be positioned such that air gaps are presentbetween the trim structure 156 and adjacent display panel structures toprevent electrostatic discharge damage. As shown in FIG. 11 , trimstructure 156 is separated from substrate 160 by gap 182 in theX-direction and gap 184 in the Z-direction. Gaps 182 and 184 may begreater than 5 micron, greater than 10 micron, greater than 20 micron,greater than 50 micron, greater than 100 micron, between 10 micron and50 micron, etc. Trim structure 156 may be formed from a plastic materialin some embodiments. Alternatively, trim structure 156 may be formedfrom a conductive material and electrically connected to housing 12Ausing a conductive adhesive 178. This type of arrangement may provide anelectrostatic discharge path from trim structure 156 to housing 12A(through adhesive 178).

FIG. 12A is a top view of lower housing 12B of electronic device 10. Aspreviously discussed, lower housing 12B includes a keyboard 8 and atouch-sensitive area (touch pad) 6. To maintain the structural integrityof lower housing 12B and the input-output devices (e.g., keyboard 8 andtouchpad 6) in the lower housing 12B, wall structures may be included inthe interior of housing 12B. The wall structures may be aligned with thelower edge of keyboard 8 and the left and right edges of touch pad 6.The wall structures may have a footprint that results in the lowerhousing 12B having a high rigidity in region 186 of the housing. Therigidity of housing 12B (and associated internal components) is higherin region 186 than in surrounding portions of housing 12B. Region 186has a first portion that extends along (and overlapping) a lower edge ofkeyboard 8, a second portion that extends from the first portion andorthogonal to the first portion along (and overlapping) a left edge oftouchpad 6, and a third portion that extends from the first portion andorthogonal to the first portion along (and overlapping) a right edge oftouchpad 6.

The high-rigidity portion 186 may have the potential to cause damagedisplay 14 in upper housing 12A in an impact event. To prevent damage ofthis type, housing 12A may include a foam structure. FIG. 12B is a topview of an upper housing 12A with a foam structure. As shown, foamstructure 188 is formed in upper housing 12A. The foam structure 188 maybe, for example, embedded in a pocket in the rear wall 146 of housing12A. The rear wall of housing 12A may cover foam structure 188 on bothsides in one possible arrangement. Alternatively, rear wall portion 146of housing 12A may cover foam structure 188 on the exterior side of thedevice but not the interior side of the device. In other words, foamstructure 188 may be exposed at the interior of the device if desired.

As shown in FIG. 12B, foam 188 has a footprint that overlaps thefootprint of high-rigidity region 186 in lower housing 12B (shown inFIG. 12A). When the laptop computer of FIG. 1 is closed, foam 188 alignswith and overlaps high-rigidity region 186. Having the foam in this areamay prevent damage to display 14 during operation of the electronicdevice. For example, during an impact event on upper housing 12A whenthe laptop computer is closed, damage to the display is mitigated byfoam 188.

To further improve the mechanical strength of the electronic device, thepocket in display housing 12A that contains foam 188 may be formed withrounded corners to prevent high stress concentration areas from forming.

FIG. 13 is a top view of an illustrative LED array with LEDs 38 formedacross printed circuit board 50. As shown, LEDs 38 may be distributedacross an active area (AA) of the display. The active area is thefootprint of the display that actually emits light, and may optionallybe defined by an opaque masking layer in the display stack-up. Herein,the display panel, printed circuit board, backlight unit, optical films,and other desired display layers may all be referred to as having anactive area. The active area of each layer may simply refer to thefootprint of each layer that overlaps with the light-emitting area ofthe display. In the example of FIG. 13 , the active area hasright-angled corners and a notch 62. This example is merelyillustrative. In general, the active area may have any desired shape.Printed circuit board 50 may have an inactive area (e.g., an area thatdoes not vertically overlap the light-emitting footprint of the display)in addition to the active area.

In addition to LEDs being mounted on printed circuit board 50,additional electronic components 190 (sometimes referred to as surfacemount components) may be mounted to printed circuit board 50. Theprinted circuit board may have an edge 50E in the inactive area thatincludes components 190. Components 190 may include, for example,driving circuitry (e.g., one or more display driver integrated circuits)that is used to control LEDs 38 in the LED array. Components 190 may beattached to the upper surface of the printed circuit board using solder.As shown in FIG. 13 , the components 190 are consolidated in one edge50E of the printed circuit board. This allows only one edge of theprinted circuit board to have a larger gap between the edge of theprinted circuit board and the active area (e.g., distance 192 in FIG. 13). The remaining three edges of the printed circuit board have a smallergap between the edge of the printed circuit board and the active area(e.g., distance 194 in FIG. 13 ). In other words, distance 194 is lessthan distance 192.

During a drop or impact event, one or more optical films 26 in thebacklight unit may shift into the edge of the printed circuit board withthe electronic components 190. If care is not taken, one of the opticalfilms may strike an electronic component 190 and dislodge the electroniccomponent from the printed circuit board. To ensure the reliability ofelectronic components 190, a mechanical structure may be included alongthe edge of the printed circuit board to prevent the electroniccomponents from being dislodged or damaged during a drop event.

FIG. 14 is a cross-sectional side view of display 14. As shown in FIG.14 , substrate 50 (for LED array 36) extends across the display parallelto the rear wall of housing 12A. An array of LEDs is mounted onsubstrate 50. Additionally, along the edge 50E of substrate 50,additional electronic components 190 are mounted.

Display panel 24 may be mounted to a stiffening component 196.Stiffening component 196 may sometimes be referred to as a chassis,stiffener, bracket, etc. Chassis 196 may have a first portion (e.g.,portion 196-1) parallel to substrate 50, the rear housing wall, and theXY-plane that serves as a mounting substrate for display panel 24. Inother words, an edge of the display panel 24 is mounted on portion 196-1of component 196 (as shown in FIG. 14 ). Component 196 may be formedfrom metal (e.g., stainless steel) and may have a high rigidity.

To protect electronic components 190 along the edge 50E, chassis 196includes an additional portion 196-2 that is orthogonal to substrate 50,the rear housing wall, portion 196-1, and the XY-plane. Portion 196-2 isparallel to the XZ-plane. Portion 196-2 extends between the edge ofoptical films 26 and electronic components 190. Portion 196-2 thereforeserves as a physical barrier that prevents optical films 26 fromstriking electronic components 190. If a drop event causes optical films26 to shift in the negative Y-direction, the optical films will beblocked by portion 196-2 of chassis 196 (and thus not reach or contactelectronic components 190 along edge 50E of substrate 50).

FIG. 15 is a cross-sectional side view of an illustrative colorconversion layer 34 with scattering dopants for increasing the amount ofoff-axis blue light. As shown in the inset portion of FIG. 15 , redquantum dots 112-R output light in a random direction (e.g., thedirection that red light is output is not correlated to the directionthat blue light is received). Similarly, green quantum dots 112-G outputlight in a random direction (e.g., the direction that green light isoutput is not correlated to the direction that blue light is received).To make the emission direction of blue light more random (and thereforeequalize the off-axis emission of blue light to the off-axis emission ofred and green light), scattering dopants 130 may be included in thephosphor layer. Scattering dopants 130 may elastically scatter bluelight. This means that no energy is lost when the scattering dopants 130receive blue light and that the wavelength of the light is not changedby the scattering dopants. However, the scattering dopants randomize thedirection of the blue light. The blue light will be scattered by thescattering dopants while the red and green light will tend not to bescattered by the scattering dopants. Consequently, the distribution ofred, blue, and green light may be equalized both on-axis and off-axis.

The average diameter of the scattering dopants may be between 5 and 20nanometers, less than 500 nanometers, less than 100 nanometers, lessthan 50 nanometers, less than 20 nanometers, more than 5 nanometers,more than 1 nanometer, or any other desired diameter. The averagediameter of quantum dots 112-R and 112-G may be more than 500nanometers, more than 1 micron, more than 2 microns, between 1 and 3microns, less than 5 microns, or any other desired diameter.

The quantum dots 112-R and 112-G as well as scattering dopants 130 maybe distributed in a resin 132 (sometimes referred to as host resin 132).Resin 132 may have an index of refraction of less than 1.5, less between1.45 and 1.55, less than 1.6, less than 1.55, greater than 1.4, between1.4 and 1.6, or any other desired index of refraction. To achieve thedesired scattering using the scattering dopants, the scattering dopantsmay be formed using a transparent material that has an index ofrefraction that is greater than 1.5, greater than 1.55, greater than1.6, greater than 1.65, greater than 1.7, between 1.6 and 1.7, between1.55 and 1.7, or any other desired index of refraction. The differencein refractive index between resin 132 and scattering dopants 130 may begreater than 0.05, greater than 0.1, greater than 0.15, greater than0.2, between 0.1 and 0.2, between 0.15 and 0.2, or any other desiredmagnitude.

In general, the scattering dopants may be formed from any desiredmaterial (e.g., silicone, melamine, etc.). As one example, thescattering dopants may be formed from melamine (C₃H₆N₆, having an indexof refraction of 1.66) whereas the resin 132 may have a refractive indexof 1.49. The density of scattering dopants 130 within the phosphor layermay be less than 10 g/m³, less than 5 g/m³, less than 3 g/m³, less than2 g/m³, more than 1 g/m³, more than 2 g/m³, more than 3 g/m³, between 1g/m³ and 3 g/m³, between 1.5 g/m³ and 2.5 g/m³, between 1 g/m³ and 5g/m³, or any other desired density.

It should be noted that the example of including red and green quantumdots in the color conversion layer is merely illustrative. In general,any desired red/green color conversion materials may be included (e.g.,red and green phosphor, quantum dots, perovskite, etc.).

Returning to FIG. 3 which shows LED cells 38C, the light from the edgeof a cell 38C tends to have been recycled more than light emitted fromthe center of the cell. Therefore, light from the edge of the cell maybe less blue than light from the middle of the cell. FIG. 16 is a graphillustrating this effect. As shown by curve 442 in FIG. 16 , light fromthe center of cell is bluer than light from the edges of the cell. Theshape of the profile shown in FIG. 16 is merely illustrative. Ingeneral, the profile may have any desired shape.

Within the display (e.g., the middle of the display), light from a givencell is mixed with light from neighboring cells to produce display lightof a uniform color (with a particular amount of blue light). However, atthe edges of the display, there may be a shortage of yellow light(because at an edge, yellow light from a neighboring cell is absent atthe border). This makes light from the edge of the display bluer thanlight from the middle of the display. This effect is shown in the graphof FIG. 17 . As shown by curve 444, light from the edge of the displayis bluer than light from the middle of the display. Each mark along theX-axis indicates the border of a respective cell 38C. As shown, lightexiting from the two cells closest to the edge of the display is bluerthan the remaining cells in the display. This example is merelyillustrative, and light exiting from any desired number of cells may bebluer than the remaining cells in the display depending on the specificdisplay design. The curve shown in FIG. 17 is merely illustrative andmay have a different shape if desired.

To mitigate the color non-uniformity of the emitted light from thedisplay, color conversion layer 34 may have non-uniformities across theactive area of the display. In FIG. 15 , phosphor layer 40 has a uniformthickness (e.g., the dimension in the Z-direction is uniform across thephosphor layer). To mitigate non-uniformities, the phosphor may insteadhave varying thickness.

FIG. 18 is a graph showing how a color conversion layer property mayvary across the width of a cell in LED array 36. The property may followprofile 200. In the example of FIG. 18 , the cell has two light-emittingdiodes along the width of the cell. For example, the cell may includefour total light-emitting diodes arranged in a 2×2 grid. Profile 200 hasa local maximum over each light-emitting diode. Between thelight-emitting diodes (e.g., in portions not overlapping thelight-emitting diodes), the profile dips and the property has a lowermagnitude.

Consider the example where phosphor thickness is the varied propertyshown in FIG. 18 . In the areas over the LEDs, the phosphor thickness isgreater than in portions between the LEDs. The greater phosphorthickness results in more blue light being converted to red and greenlight, mitigating the high bluishness of the light over the LEDs (asshown in FIG. 16 ).

Phosphor thickness is merely one property of many that may be varied inthe color conversion layer to increase the uniformity of light in thedisplay. As other examples, the concentration of red quantum dots 112Rmay be the varied property in FIG. 18 (with a higher concentration ofred quantum dots over the LEDs), the concentration of green quantum dots112G may be the varied property in FIG. 18 (with a higher concentrationof green quantum dots over the LEDs), the concentration of scatteringparticles 130 may be the varied property in FIG. 18 (with a higherconcentration of scattering particles over the LEDs), the recyclingpercentage achieved by light-redirecting structures 102-4 may be thevaried property in FIG. 18 (with the light-redirecting structures havinga shape that results in higher recycling percentage over the LEDs thanin portions not overlapping the LEDs), etc.

FIG. 19 is a graph showing how a color conversion layer property mayvary across the width of the display. The property may follow profile202. In the example of FIG. 19 , profile 202 increases towards the edgeof the display.

Consider the example where phosphor thickness is the varied property asshown in FIG. 19 . Towards the edge of the LED array, the phosphorthickness is greater than in portions in a central area of the LEDarray. The greater phosphor thickness results in more blue light beingconverted to red and green light, mitigating the high bluishness of thelight in the edges of the display (as shown in FIG. 17 ).

Phosphor thickness is merely one property of many that may be varied inthe color conversion layer to increase the uniformity of light in thedisplay. As other examples, the concentration of red quantum dots 112Rmay be the varied property in FIG. 19 (with a higher concentration ofred quantum dots at the edges of the color conversion layer), theconcentration of green quantum dots 112G may be the varied property inFIG. 19 (with a higher concentration of green quantum dots at the edgesof the color conversion layer), the concentration of scatteringparticles 130 may be the varied property in FIG. 19 (with a higherconcentration of scattering particles at the edges of the colorconversion layer), the recycling percentage achieved bylight-redirecting structures 102-4 may be the varied property in FIG. 19(with the light-redirecting structures having a shape that results inhigher recycling percentage at the edges of the color conversion layerthan at a central portion of the color conversion layer), etc.

In FIGS. 18 and 19 , profiles 200 and 202 both have gradual changes.This example is merely illustrative. The profiles may instead have oneor more step changes if desired. In general, profiles 200 and 202 mayhave any desired shapes.

The techniques of FIG. 18 (e.g., intra-cell color conversion layernon-uniformity) and the techniques of FIG. 19 (e.g., inter-cell colorconversion layer non-uniformity) may both be used in a single colorconversion layer if desired.

When the phosphor layer has a varying thickness, the additional film 108formed over the phosphor layer may also have a varying thickness suchthat the additional film has a planar upper surface (as shown in FIG.20A). Alternatively, the color conversion layer 34 may be embossed suchthat the phosphor layer 40 has a varying thickness and additional film108 has a uniform thickness across the color conversion layer (as shownin FIG. 20B).

FIG. 21 is a cross-sectional side view of an illustrative colorconversion layer 34 that includes light-redirecting structures having avarying shape. In other words, for the color conversion layer 34 in FIG.21 , the recycling percentage of the light-redirecting structures is theproperty that varies as in FIG. 18 or FIG. 19 . A first subset 204-1 ofthe light-redirecting structures may have a first shape with a firstcorresponding reflectance (e.g., reflectance of light received fromunderlying optical films, sometimes referred to as the recyclingpercentage). A first second 204-2 of the light-redirecting structuresmay have a second shape with a second corresponding reflectance(recycling percentage). The shapes of the light-redirecting structuresmay change according to a step function or may gradually change.

The examples of FIGS. 18-21 to mitigate color non-uniformity in thebacklight unit are merely illustrative. Instead or in addition to thesetechniques, a color conversion material may be formed on encapsulantlayer 52 of LED array 36. FIG. 22 is a cross-sectional side view showingan arrangement of this type. In this example, color conversion layer 34is uniform across the display. The color non-uniformity is mitigatedusing color conversion patches 206 that are formed on an upper surfaceof encapsulant 52 over LEDs 38. The color conversion patches may convertthe color of light emitted by LEDs 38 (e.g., blue) to a different color(e.g., white). In other words, the wavelength of light having the peakbrightness is different for light received by color conversion patches206 than light exiting the color conversion patches. The colorconversion patches may be formed from ink, quantum dots (as in phosphorlayer 40), or any other desired material.

In FIG. 22 , the color conversion patches 206 are formed in recesses inan upper surface 208 of encapsulant 52. In this arrangement, some or allof color conversion patches 206 may be formed beneath a plane defined byupper surface 208. In one example, shown in FIG. 22 , the upper surfaceof patches 206 and upper surface 208 are coplanar (thus defining asmooth, continuous upper surface). As another possible arrangement,encapsulant 52 may have a planar upper surface without recesses. Thecolor conversion patches 206 are then formed on the upper surface (e.g.,above the plane defined by surface 208). Regardless of whether the colorconversion patches are formed entirely below upper surface 208,partially below upper surface 208 and partially above upper surface 208,or entirely above upper surface 208, the color conversion patches 206may have either a uniform thickness or a non-uniform thickness (as inFIG. 22 ).

As shown in FIG. 4 , color conversion layer 34 includeslight-redirecting structures 102-4 on an upper surface of film 108.Brightness-enhancement film 44-1 includes light-redirecting structures110-1 on an upper surface of film 114-1. Brightness-enhancement film44-2 includes light-redirecting structures 110-2 on an upper surface offilm 114-2. Due to this arrangement, the lower surface of film 114-1 maybe susceptible to being scratched by the tips of light-redirectingstructures 102-4, the lower surface of film 114-2 may be susceptible tobeing scratched by the tips of light-redirecting structures 110-1, andthe lower surface of film 30 may be susceptible to being scratched bythe tips of light-redirecting structures 110-2. Scratching of this typemay result in damage to the optical films that causes optical artifactsin the display.

To mitigate scratching caused by protrusions within the backlight unit,the protrusions may have rounded tips. FIG. 23 is a cross-sectional sideview of an illustrative light-redirecting structure 102-4. As shown inFIG. 23 , each light-redirecting structure 102-4 has a rounded tip 210.Rounded tip 210 may be less likely to scratch the overlying film thanwhen a non-rounded tip is used.

Rounded tip 210 may have a radius of curvature that is greater than 0.3microns, greater than 0.4 microns, greater than 0.5 microns, greaterthan 0.7 microns, greater than 1.0 micron, less than 1.5 microns, lessthan 3 microns, less than 1.0 micron, between 0.4 microns and 1.5microns, etc.

FIG. 24 is a cross-sectional side view of an illustrative backlight unitshowing how light-redirecting structures 102-4 in color conversion layer34 and light-redirecting structures 110-1 in brightness-enhancement film44-1 may both have rounded tips similar to as shown in FIG. 23 . Therounded tips of both structures 102-4 and 110-1 may have a radius ofcurvature that is greater than 0.3 microns, greater than 0.4 microns,greater than 0.5 microns, greater than 0.7 microns, greater than 1.0micron, less than 1.5 microns, less than 3 microns, less than 1.0micron, between 0.4 microns and 1.5 microns, etc. Structures 102-4 and110-1 may have rounded tips regardless of whether structures 102-4 and110-1 have a pyramidal shape (e.g., with a square base and fourtriangular faces that meet at a vertex), a triangular pyramidal shape(e.g., with a triangular base and three triangular faces that meet at avertex), a partial-cube shape (e.g., corner-cubes by three square facesthat meet at a vertex), a tapered pyramid structure, an elongatedstructure (as discussed earlier in connection with structures 110-1 and110-2), etc.

In some cases, light-redirecting structures 110-2 may have rounded tipssimilar to as shown in FIG. 23 (and in structures 110-1 and 102-4 inFIG. 24 ). However, scratching the underlying surface of diffusion film30 may not produce detrimental optical artifacts in the display.Therefore, structures 110-2 may have sharp tips (e.g., not roundedtips). Said another way, the radius of curvature of the tips ofstructures 110-2 may be less than the radius of curvature of the tips ofstructures 110-1 and 102-4 (e.g., by greater than 0.1 microns, greaterthan 0.2 microns, greater than 0.3 microns, greater than 0.4 microns,greater than 0.5 microns, greater than 0.7 microns, greater than 1.0micron, less than 1.5 microns, less than 3 microns, less than 1.0micron, between 0.4 microns and 1.5 microns, etc.). The radius ofcurvature of the tips of structures 110-2 may be less than 0.1 microns,less than 0.2 microns, less than 0.3 microns, less than 0.4 microns,etc.

In addition to preventing scratching, the rounded tips of structures110-1 and 102-4 may reduce the coefficient of friction between theadjacent optical films in the backlight unit (e.g., between films 34 and44-1 and between films 44-1 and 44-2). This reduction in friction mayreduce the likelihood of the optical films wrinkling during operation ofthe device (e.g., due to shifting from an impact event or thermalexpansion). The coefficient of friction between adjacent optical filmsmay additionally be reduced by including clear dots 212 on the bottomsurface of base film 114-1 and/or 114-2. The clear dots 212 may beoptically invisible (e.g., the clear dots do not impact the opticalperformance of the backlight). However, the clear dots 212 furtherreduce the coefficient of friction between adjacent optical films in thebacklight unit. The clear dots may have a uniform distribution acrossthe optical films (e.g., distributed evenly across a given opticalfilm), may be concentrated at an edge of the optical films (e.g.,included in a ring shape around the periphery of a given optical filmbut not in a central portion of that optical film), etc. The clear dots212 may be formed from clear ink or any other desired material.

FIG. 25 is a cross-sectional side view of an illustrative light-emittingdiode in LED array 36. As shown, LED 38 may be mounted on substrate 50.LED 38 may have conductive contact pads 214 that are physically andelectrically connected to respective conductive contact pads 216 onsubstrate 50 by solder 218. Each light-emitting diode may be formed in arespective package (e.g., that includes sapphire) that is attached tothe substrate 50.

A distributed Bragg reflector (DBR) 220 may be included over an uppersurface of each LED 38. In some cases, DBR 220 may reflect substantiallyall light generated by LED 38 such that the LED serves as a side-emitter(and emits light primarily in a direction that is parallel to theXY-plane and substrate 50). Alternatively, the reflectance of DBR 220may be tuned to allow some but not all light to pass through DBR 220.For example, angled light 222 may pass through DBR 220 instead of beingreflected.

The tuning of DBR 220 may result in LED 38 having a peak emission angle224 (e.g., the angle relative to the substrate 50 and XY-plane with thehighest intensity of emitted light from LED 38) that is greater than 0degrees, greater than 10 degrees, greater than 20 degrees, greater than30 degrees, greater than 45 degrees, greater than 60 degrees, greaterthan 70 degrees, less than 10 degrees, less than 20 degrees, less than30 degrees, less than 45 degrees, less than 60 degrees, less than 70degrees, less than 90 degrees, between 5 degrees and 85 degrees, between5 degrees and 45 degrees, between 1 degree and 30 degrees, between 45degrees and 85 degrees, between 60 degrees and 89 degrees, etc. TuningDBR 220 in this manner may increase the efficiency of the display(relative to arrangements where LED 38 is a side-emitter).

A reflective layer 226 may be formed on an upper surface of substrate 50to increase the efficiency of the display. Reflective layer 226 may havea reflectance that is greater than 60%, greater than 70%, greater than80%, greater than 90%, greater than 95%, greater than 99%, etc.Reflective layer 226 may be formed from any desired material (e.g., awhite solder resist layer). Each LED may be formed in a respectiveopening in reflective layer 226.

To mitigate hotspots in the display caused by LEDs 38, encapsulant 52may have recesses formed over the LEDs. FIG. 26 is a cross-sectionalside view of an illustrative backlight unit 42 of this type. As shown inFIG. 26 , a recess 228 is formed over each LED 38 within LED array 36.Each recess increases the amount of light from LED 38 that is reflectedvia total internal reflection (at the encapsulant-air interface). Thisbetter disperses light from LED 38 within the XY-plane, mitigatinghotspots caused by the LEDs.

Recesses 228 may have any desired shape. In FIG. 26 , the recesses 228have a conical shape. In other words, an edge surface 230 extends in acircle (or oval) around the footprint of LED 38. This example is merelyillustrative. FIG. 27A shows an alternate example where recess 228 has asemi-spherical shape (e.g., the recess has spherical curvature). In FIG.26 , the conical shape of recesses 228 terminates at a flat surface 232.This example is merely illustrative. FIG. 27B shows an alternate examplewhere recess 228 has a conical shape with an edge surface 230 that meetsat a vertex (instead of a flat surface as in FIG. 26 ).

In FIG. 27C, edge surfaces 230 of the recess are curved and meet at avertex. In FIG. 27D, edge surfaces 230 of the recess are curved and meetat a flat surface 232. Recess 228 may have multiple portions withdifferent widths. In the example of FIG. 27E, a first portion of therecess has a first width 234 whereas a second portion of the recess hasa second width 236. The second (lower) portion may have a smaller widththan the first (upper) portion of the recess. In other words, width 236is smaller than width 234.

In general, each encapsulant recess 228 may have any desired shape.Regardless of the shape of the recess, a portion of encapsulant 52 mayremain present between an upper surface of LED 38 (and DBR 220) and therecess. The width of each recess may be greater than the width of theLED, may be greater than the 1.5 times the width of the LED, may begreater than the 2 times the width of the LED, may be less than the 3times the width of the LED, etc.

Regardless of the shape of the recess, the recess may optionally befilled by a filler material 238 (as shown in FIG. 27A, for example). Thefiller material may be a gray ink or a color conversion material, aspossible examples. When the filler material is omitted, the recesses mayinstead be filled with air.

Incorporating recesses of the type shown in FIGS. 26 and 27 may mitigatehotspots cased by LEDs 38 in LED array 36. This may allow one or moreoptical films to be omitted from the backlight unit, reducing thethickness, manufacturing cost, and manufacturing complexity of thedisplay. For example, when recesses 228 are included in encapsulant 52,only five or six optical films may be needed to provide sufficientlyuniform backlight to display panel 24 (instead of seven as in FIG. 4when no encapsulant recesses are included).

As shown in FIG. 26 , an opaque dam 240 may optionally be formed betweenadjacent LEDs in LED array 36. Alternatively, opaque dam 240 may beformed at the border between adjacent LED cells 38C (see FIG. 3 ). Dam240 may have the same thickness 242 as encapsulant 52 or may have asmaller thickness than encapsulant 52 (such that the encapsulant isformed over and covers an upper surface of each dam 240).

An air gap may also be formed in place of dam 240. The air gap mayextend completely through encapsulant 52 (such that the encapsulant hasa thickness 242 of 0) or only partially through encapsulant 52 (suchthat the encapsulant has a non-zero thickness 242 overlapped by the airgap).

FIG. 28 is a top view of LED array 36 showing how the pitch of the LEDsand/or the dams may be adjusted to mitigate non-uniformities in thedisplay. As shown in FIG. 28 , the LEDs 38 in LED array 36 are arrangedin a plurality of cells 38C. In the example of FIG. 28 , each cellincludes a 2×2 grid of LEDs 38. The LEDs have a horizontal pitch 244 anda vertical pitch 246. Cells 38C are defined by dams (e.g., opaque dams)that have a horizontal pitch 248 and a vertical pitch 250.

The display may be susceptible to having a lower than desired luminanceat the edges. To mitigate this non-uniformity, the pitch of the LEDsand/or dams may be reduced at the edges of the display. In the exampleof FIG. 28 , there are m rows and n columns of LED cells 38C. Theleft-most column of LED cells (COL 1) and the right-most column of LEDcells (COL N) may have a lower horizontal dam pitch 248 (and,correspondingly, a lower cell width) than the remaining, central columnsof LED cells. Similarly, the row of LED cells that is below notch 62(ROW 2) may have a lower vertical dam pitch 250 (and, correspondingly, alower cell height) than the remaining, central rows of LED cells. Thefinal row of LED cells in the LED array (not explicitly shown in FIG. 28) may also have a lower vertical dam pitch 250 than the remaining,central rows of LED cells. Reducing the dam pitch adjacent to the edgesof the display in this manner may mitigate non-uniformities at the edgesof the display.

In FIG. 28 , the vertical dam pitch 250 in the first row of LED cells(that is interrupted by the notch) is larger than the row 2 vertical dampitch and the vertical dam pitch of the central rows. The vertical dampitch in the first row is set to match the height 252 of notch 62. Thisexample is merely illustrative. In an alternate arrangement, multiplerows of LED cells 38C may be interrupted by notch 62 (instead of just 1as in FIG. 28 ) and those rows of LED cells 38C may have a vertical dampitch 250 that is lower than the notch height 252.

In the example of FIG. 28 , LEDs 38 have a uniform pitch across the LEDarray (whether or not the LEDs are in the smaller edge cells).Alternatively, the LEDs 38 at the edge of the array (e.g., in thesmaller edge cells) may also have a smaller LED pitch (in the horizontaland/or vertical direction) than in the central portion of the array.

FIGS. 29-31 show adhesive layers that may be used to attach LED array 36to display housing 12A. FIG. 29 is a cross-sectional side view of device10. As shown, a first adhesive layer 254 is attached to a lower surfaceof LED array 36 (e.g., a lower surface of substrate 50 in LED array 36).Adhesive layer 254 (sometimes referred to as spacer layer 254) may be asingle-sided adhesive where the surface coupled to LED array 36 isadhesive and the opposing surface is not adhesive. A plurality ofadhesive strips 256 attach spacer layer 254 to rear wall 146 of housing12A. Adhesive strips 256 may be formed from discrete, elongated, anddouble-sided adhesive strips. A first side of each adhesive strip isattached to spacer 254 and a second side of each adhesive strip isattached to an interior surface of the rear wall of housing 12A.

Additionally, a conductive adhesive 258 may be attached between aninterior surface of the rear wall of housing 12A and LED array 36 (e.g.,a lower surface of substrate 50 in LED array 36). Specifically, theconductive adhesive 258 may be physically and electrically connected toa ground trace 260 in LED array 36. Ground trace 260 may extendpartially or completely around the periphery of LED array 36. Conductiveadhesive 258 therefore electrically connects ground trace 260 to housing12A (which may be conductive and serve as a ground structure). Theconductive adhesive 258 has a thickness that is equal to the sum of thethickness of adhesive layer 254 and the thickness of adhesive strips256. In addition to serving as a grounding structure, conductiveadhesive 258 may mitigate undesired electrostatic discharge in device10.

Adhesive layer 256 may be formed in strips (instead of a continuousplane like layer 254) to increase the reworkability of the display. Inother words, stretching and heating may be used to deliberately removeadhesive strips 256 if desired.

Adhesive layer 254 may be formed from a layer having a low dielectricconstant to mitigate parasitic capacitances and corresponding systempower loss. The dielectric constant of adhesive layer 254 may be lessthan 10, less than 6.0, less than 5.0, less than 4.0, less than 3.0,less than 2.0, etc.

The thickness of the strips 256 (e.g., the dimension parallel to theZ-direction) may be less than 100 microns, less than 80 microns, lessthan 60 microns, greater than 30 microns, between 30 microns and 70microns, etc. The thickness of the spacer 254 (e.g., the dimensionparallel to the Z-direction) may be less than 150 microns, less than 100microns, less than 80 microns, less than 60 microns, greater than 50microns, greater than 70 microns, between 50 microns and 100 microns,etc. The thickness of the conductive adhesive 258 (e.g., the dimensionparallel to the Z-direction) may be less than 250 microns, less than 150microns, less than 100 microns, greater than 100 microns, greater than120 microns, between 100 microns and 150 microns, etc.

FIG. 30 shows how adhesive strips 256 may be elongated in theY-direction. Each strip extends along a longitudinal axis that isparallel to the Y-direction. In other words, the length of each stripmay be longer than the width of each strip and the length of each stripmay extend parallel to the Y-axis. This example is merely illustrative.The adhesive strips may instead extend parallel to the X-axis ifdesired. Each strip may have a length that is more than 3× greater thanthe width, more than 5× greater than the width, more than 10× greaterthan the width, more than 20× greater than the width, more than 50×greater than the width, etc.

FIG. 31 is a rear view of LED array 36 showing the relative positions ofconductive adhesive 258 and adhesive layer 254. As shown, conductiveadhesive 258 extends around the periphery of the LED array. In theexample of FIG. 31 , conductive adhesive 258 extends along the left,upper, and right edges of the LED array (but not the lower edge of theLED array). The conductive adhesive 258 therefore surrounds the LEDarray on three out of four sides. The footprint of ground trace 260(shown explicitly in FIG. 29 ) may be the same or approximately the sameas the footprint of conductive adhesive 258. In other words, the groundtrace 260 also surrounds the LED array on three out of four sides (alongthe left, upper, and right edges). The conductive adhesive 258 (andgrounding trace 260 may be routed around the notch 62 in LED array 36,as shown in FIG. 31 .

Adhesive layer 254 covers a central area of the LED array 36. Theadhesive layer 254 may have a notch to accommodate notch 62 in the LEDarray 36. Adhesive layer 254 may have an array of openings 264. Eachopening 264 may be a through-hole that extends entirely through theadhesive layer (e.g., from a first surface of the adhesive layer to asecond, opposing surface of the adhesive layer). The openings 264 allowfor the passage of air during the lamination process, mitigating bubbleformation. Each opening 264 may have a diameter (or width) that isgreater than 0.1 millimeters, greater than 0.5 millimeters, greater than1.0 millimeter, greater than 1.5 millimeters, greater than 3.0millimeters, less than 0.1 millimeters, less than 0.5 millimeters, lessthan 1.0 millimeter, less than 1.5 millimeters, less than 3.0millimeters, between 1.0 millimeters and 2.0 millimeters, etc. The totalnumber of openings 264 in adhesive layer 254 may be greater than 200,greater than 300, greater than 400, greater than 500, greater than 750,greater than 1000, less than 200, less than 300, less than 400, lessthan 500, less than 750, less than 1000, between 250 and 750, etc.

It should be noted that any of the adhesive layers mentioned herein(e.g., layers 82, 84, 90, 92, 152, 154, 176, 178, 254, 256, and 258) maybe formed from pressure sensitive adhesive (PSA), optically clearadhesive (OCA), liquid optically clear adhesive (LOCA), a curedadhesive, or any other desired type of adhesive.

The foregoing is merely illustrative and various modifications can bemade to the described embodiments. The foregoing embodiments may beimplemented individually or in any combination.

What is claimed is:
 1. An electronic device comprising: a liquid crystaldisplay panel; a backlight unit that provides backlight for the liquidcrystal display panel, wherein the backlight unit comprises: an array oflight-emitting diodes arranged in a light-emitting area, wherein thelight-emitting area has a notch and wherein the notch has first andsecond opposing sides; a first reflective layer that is formed on thefirst side of the notch; and a second reflective layer that is formed onthe second side of the notch; and an input-output component that isformed in the notch between the first and second reflective layers. 2.The electronic device defined in claim 1, wherein the electronic devicecomprises a housing, wherein the liquid crystal display panel and thebacklight unit are formed in the housing, and wherein the electronicdevice includes first and second protrusions that extend from thehousing.
 3. The electronic device defined in claim 2, wherein the firstreflective layer includes a first opening, wherein the second reflectivelayer includes a second opening, wherein the first protrusion extendsthrough the first opening, and wherein the second protrusion extendsthrough the second opening.
 4. The electronic device defined in claim 3,wherein the backlight unit further comprises: an optical film that isformed over the array of light-emitting diodes; a third reflective layerthat is formed on the optical film and that overlaps the firstreflective layer; and a fourth reflective layer that is formed on theoptical film and that overlaps the second reflective layer.
 5. Theelectronic device defined in claim 2, wherein the backlight unit furthercomprises: a plurality of optical films, wherein each one of theplurality of optical films has first and second respective openings thatalign with the first and second protrusions.
 6. The electronic devicedefined in claim 1, wherein the backlight unit further comprises: first,second, and third optical films that are formed over the array oflight-emitting diodes; a first adhesive patch that is formed between thefirst and second optical films and that overlaps the first reflectivelayer; a second adhesive patch that is formed between the first andsecond optical films and that overlaps the second reflective layer; athird adhesive patch that is formed between the second and third opticalfilms and that overlaps the first reflective layer and the firstadhesive patch; and a fourth adhesive patch that is formed between thesecond and third optical films and that overlaps the second reflectivelayer and the second adhesive patch.
 7. The electronic device defined inclaim 1, wherein the backlight unit further comprises: a bracket thatoverlaps the notch; and foam that is interposed between the bracket andthe liquid crystal display panel.
 8. The electronic device defined inclaim 7, further comprising: an optical film that is formed over thearray of light-emitting diodes; a first adhesive layer that isinterposed between the bracket and the optical film; and a secondadhesive layer that is interposed between the bracket and the foam. 9.The electronic device defined in claim 7, wherein the bracket has anopening that accommodates the input-output component.
 10. An electronicdevice comprising: a housing having a sidewall with an interior surface,wherein the interior surface has a first portion and a second portion; aliquid crystal display panel in the housing; and a backlight unit in thehousing that provides backlight for the liquid crystal display panel,wherein the backlight unit comprises: an array of light-emitting diodes;a plurality of optical films that is formed over the array oflight-emitting diodes, wherein an edge of the plurality of optical filmsis adjacent to the first portion of the interior surface of the sidewalland wherein the first portion has a lower reflectance than the secondportion; a substrate, wherein the array of light-emitting diodes isformed on the substrate; electronic components that are formed along anedge of the substrate; and a chassis having first and second orthogonalportions, wherein the liquid crystal display panel is mounted on thefirst portion of the chassis and wherein the second portion of thechassis extends between the plurality of optical films and theelectronic components.
 11. The electronic device defined in claim 10,wherein the edge of the substrate is a first edge, wherein the substratehas a second edge opposite the first edge, wherein a notch is formed inthe second edge, and wherein the electronic device includes aninput-output component that is formed in the notch.
 12. The electronicdevice defined in claim 10, wherein the first portion has a reflectancethat is between 35% and 45%.
 13. The electronic device defined in claim10, wherein the liquid crystal display panel further comprises: athin-film transistor substrate; and a conductive shielding ring thatextends around a periphery of the thin-film transistor substrate. 14.The electronic device defined in claim 10, further comprising: aconductive trim between the housing and the liquid crystal displaypanel; and conductive adhesive that attaches the conductive trim to thehousing.
 15. The electronic device defined in claim 10, wherein thesecond portion of the interior surface of the sidewall comprises a metalmaterial and wherein the first portion of the interior surface comprisesa laser darkened portion of the metal material.
 16. An electronic devicecomprising: a lower housing; a keyboard in the lower housing, whereinthe lower housing has a high-rigidity portion; an upper housing having ahousing wall, wherein the upper housing is coupled to the lower housingby a hinge structure; a display in the upper housing, wherein thedisplay is parallel to the housing wall; foam that is embedded in thehousing wall, wherein the foam has a footprint that is aligned with thehigh-rigidity portion of the lower housing when the lower housing andthe upper housing are parallel; and a touchpad in the lower housing,wherein the high-rigidity portion has a first portion that extends alonga lower edge of the keyboard, a second portion that extends orthogonalto the first portion along a left edge of the touchpad, and a thirdportion that extends orthogonal to the first portion along a right edgeof the touchpad and wherein the footprint of the foam has a fourthportion that is aligned with the first portion, a fifth portion that isaligned with the second portion, and a sixth portion that is alignedwith the third portion.